Apparatus for coating the interior of a container with a resinous film



Dec. 3, 1968 Filed April 23, 1965 V. J. PATTI APPARATUS FOR COATING THEINTER CONTAINER WITH A RESINOUS P IOR OF A ILM 2 Sheets-Sheet 1 BY a [5/I ATTORNEYS Dec. 3, 1968 v. J. PATTI 3,413,955

APPARATUS FOR COATING THE INTERIOR OF A CONTAINER WITH A RESINOUS FILMFiled April 23, 1965 2 Sheets-Sheet 2 IN VENTOR. ///l/C/V7 24777 BY IATTORNEYS United States Patent 3,413,955 APPARATUS FOR COATING THEINTERIOR OF A CONTAINER WITH A RESINOUS FILM Vincent J. Patti, Norridge,IIL, assignor to TRW Inc., a corporation of Ohio Filed Apr. 23, 1965,Ser. No. 450,480 3 Claims. (Cl. 118-55) ABSTRACT OF THE DISCLOSUREApparatus for coating the interior of a container with a resinous filmincluding a conveyor means, individually driven work holder means whichdeliver the container to an injecting station where the resinousmaterial is injected into the container, then to a high speed rotationstation where the work holder is driven at a high speed to distributethe resinous material as a film along the interior of the container, andfinally to a heating station where the container is driven at a lowervelocity while the resinous material is being set under the influence ofa heating means.

The present invention relates to apparatus for coating the interior ofopen ended containers with compositions settable by heat. The inventionhas particular reference to the coating of metal cans which are used asmagnetic shields about circuit elements such as coils.

In the past, some attempts have been made to shield the inner walls ofthe metallic can by lining the walls with a preformed sheet containing aferromagnetic powder dispersed through a synthetic resin or elastomer. Astrip of the preformed material would be inserted into the can in thedesired location, and then a-dhesively secured to the walls of the can.This operation was time consuming and expensive, and had its limitationswhen there was only a very small space available between the exterior ofthe coil and the inner surface of the can.

The present invention provides a means for coating cans of this typewhereby the material can be deposited as an adherent coating along theinner walls of the can. By the process of the present invention, theferromagnetic material becomes firmly bonded to the interior of the canwithout the use of adhesives. The magnetic shield which results includesa layer of set resinous material containing the ferromagnetic particlesat a heavier concentration at the interface between the coating and thecan than exists farther inwardly of the coating. The magnetic shieldthus produced reduces the magnetic shorting effect of the can and hasbeen found to significantly increase the Q of the circuit element. Thepresent invention is particularly useful in providing shields for lowfrequency IF coils which necessitate fairly large physical structuresfor the coil, and the use of a can which provides only a slightclearance between the interior wall of the can and the outer peripheryof the coil.

One of the objects of the present invention is to provide an apparatusfor coating the inside of an open ended container with a thermallysettable resinous composition, preferably including ferromagneticparticles.

Another object of the invention is to provide an apparatus forcontinuously applying a coating within the interior of an open ended canstructure.

Still another object of the invention is to provide apparatus for theinjection and distribution of a resinous composition containingferromagnetic particles along the inner periphery of a metallic can.

A further object of the invention is to provide an improved apparatusfor rapidly and controllably providing a concentration gradient offerromagnetic particles within a coating of resin deposited inside anopen ended magnetic shield.

Still another object of the invention is to provide apparatus for makingan improved shield for coils and the like which contains a resinouscomposition bonded to the inner walls of the container and containingmore ferromagnetic particles at the surface abutting the can wall thanexist further inwardly of the coating.

The present invention involves first injecting a heat settable resinouscomposition containing ferromagnetic particles into the open endedcontainer, followed by spinning the container to distribute the resinoussuspension by centrifugal force along the inner walls of the container.This centrifugal action also serves to force the relatively heavierferromagnetic particles closer to the interface of the coating and thecan, so that a relatively high concentration of ferromagnetic particleexists at such interface. After the coating has been distributed, theentire assembly is heated so that it reaches a temperature at which thesynthetic resinous material is set to a hardened form. This heating ispreferably carried out while the container is being rotated at a speedsomewhat less than the speed used for the centrifugal distribution ofthe material, but high enough so that there is no sagging of the coatingduring heating, and the heating is uniformly applied to all surfaces.

The apparatus described above lends itself readily to automaticoperation. In a preferred form of the invention, the apparatus consistsof a conveyor carrying a plurality of motors in spaced relation, withwork holding means being secured to each of the motors. A container tobe coated is mounted in axially snug fitted relation on each of the workholders. and then passed to an injection station where a nozzle isautomatically inserted into the container, and a predetermined amount ofthe resinous composition is injected through the nozzle and into thecontainer. Then, the container moves to an energizing station positionedto energize each of the motors to operate at a high rotational speed sothat the composition deposited in the container is distributed along thewalls of the container by centrifugal action. Finally, the containerwith the redistributed resinous material is heated, preferably by meansof an open flame, so that the composition is set to a solid form withinthe container.

The heat settable composition used in accordance with the presentinvention need not be a thermosetting resin where the chemical settingof the resin is accomplished by the addition of heat. While suchthermosetting resins can be used, I prefer to employ a thermoplasticcomposition which consists of a plastisol loaded with ferromagneticparticles. Such plastisols are dispersions of polyvinyl chloride resinparticles in a plasticizer preferably an alkyl phthalate such as dioctylphthalate, or isobutyl phthalate. Still other families of plasticizersuseful for polyvinyl chloride resins include the adipates, oleates,stearates, sebacates, azelates, phosphates, and citrates.

The polyvinyl chloride compositions preferably include stabilizers whichprevent any change of properties during processing of the resin. Typicalstabilizers for polyvinyl chloride are the barium cadmium carboxy-lates,bariumcadmium complexes, and the like.

A typical polyvinyl chloride plastisol for use in accordance with thepresent invention has a viscosity of about 600 centipoises at 20 C.before loading with the ferromagnetic particles. The ferromagneticparticles, preferably metallic iiron, constitute about by weight of thefinal composition, and may range from about 70 to by weight. At too highan iron concentration, the material becomes too hard to feed, while attoo low an iron concentration, the desired electrical properties arediminished.

A further description of the present invention will be 3 made inconnection with the attached sheets of drawings in which:

FIGURE 1 is a view in elevation of an assembly useful for the purposesof the present invention;

FIGURE 2 is a cross-sectional view taken substantially along the lineIIII of FIGURE 1 on an enlarged scale;

FIGURE 3 is a view taken substantially along the line III-III of FIGURE1; and

FIGURE 4 is a greatly enlarged cross-sectional view of a metallic cancoated in accordance with the procedure of the present invention.

As shown in the drawings:

In FIGURE 1, reference numeral indicates generally an assembly forcoating the interior of cans to be used for enclosing coils. Theassembly 10 includes spaced conveyor chains 11 between which there issupported a plurality of individual drive motors 12 in spaced relation.The chains 11 are driven by means of sprockets 13 and 14, with aplurality of smaller diameter idler sprockets 16, 17 and 18 beingarranged within the loop formed by the chains 11.

The entire assembly is supported on a table 19 which also supports amaterial pump 21 which serves to agitate the dispersion of ferromagneticparticles in the plastisol before being introduced into the coatingportion of the apparatus. A motor 22 is mounted above the pump 21 todrive the same. A drain valve 23 is provided to selectively dischargematerial from the pump 21, and a recirculating line 24 is provided tokeep the settable composition circulating at all times when the materialis being passed to the coating station.

The coating material is pumped by the pump 21 through a conduit 26 intoa metering ejector 27 which feeds an injector coating device generallyindicated at reference numeral 28, the coating device being best shownin FIG- URE 2 of the drawings, and including an air cylinder 29 shown inFIGURE 1. The function of the metering ejector 27 is to provide apredetermined amount of coating composition to the injector stationwhere it is injected into the can.

The individual motors 12 are supported on platforms 31 extending betweenthe spaced chains 11. The entire assembly is timed, as by means of aGeneva movement which drives the sprockets 13 and 14 to move the motors12 individually into the injecting station, then to a high speedcentrifuging station, and finally to a flame curing station, the dwelltime at each station being only a matter of a few seconds.

Each of the motors 12 has a drive shaft 32 (FIGURE 2) on which there ismounted an arbor 33 of suitable size so that it receives a can 34 insnugly fitting axial engagement against a shoulder 35 formed thereon.The arbor 33 has a pointed nose portion 36 which has the function ofassisting the distribution of the material, and shaping the end of thecoating as indicated by the beveled surface 37 in FIGURE 4.

The drive system positions the individual cans 34 'in the injectingstation in timed sequence. An electric eye 41 and a light source 42 areprovided at the injecting station, the light source 42 projecting a beamof light to the electric eye system 41. When this beam of light isinterrupted by the presence of a can 34 on an arbor 33, the injectingsystem is put into operation, the system including a reciprocablecarriage 44 carrying a nozzle 46 and insertable into the can through anaperature 47 best seen in FIGURE 4 of the drawings. The aperature 47 isprovided in the can 34 to receive an adjusting tool for adjusting theinductance of the coil contained therein when the can is used as ashield for an IF coil.

The reciprocating carriage 44 is secured to a shaft 48 operated by theair cylinder 29. A feed line 49 from the metering ejector 27 delivers apredetermined mass of material through the line 49 and into an axialbore 51 ing exit port 52. The ejector 27 is operated in timed relationto the movement of the cans and the movement of the carriage 44 so thata viscous mass 53 of resin heavily loaded with ferromagnetic particlesis deposited in the interior of the can 34. The injection normally takesabout 1 to 2 seconds after which the reciprocating carriage is withdrawnby the action of the air cylinder 29.

During the next incremental movement of the conveyor system, when a newcan is positioned for injection of the resinous material, the canpreviously coated is moved to a first energizing station where it isrotated at a high velocity in order to distribute the mass 53 along thewalls of the can and completely filling the corners. For this purpose,each of the motors 12 is provided with a pair of feeler arms 56 whichextend between the chains 11 and are arranged to engage a pair of spacedbus bars 57. The bus bars make electrical contact with the feeler arms56 and thereby drive the motor 12 at a sufficiently high velocity tocause centrifugal force to distribute the mass 53 as a fairly uniformcoating about the inner wall of the can 34. The actual speed of rotationdepends, of course, on the viscosity of the mass 53, and the dimensionsof the can 34, but for a can of /2 inch square cross-section, suitablevelocities for this step range from about 3,000 to 7,000 r.p.m. Toprovide an additional gripping on the can at such high rotationalvelocities, the arbor 43 is provided with a pair of lugs 58 and 59 onopposite sides thereof, the two lugs being pivoted at pivot points 61and 62, respectively. When the shaft 32 goes up to full rotationalspeed, the mass of the lugs 58 and 59 is distributed such that theirrespective nose portions 63 and 64 are urged toward the can and tend tobite in on the can 34, to hold it rigidly against the arbor 33.

The feeler arms 56 of each motor 12 remain engaged with the bus bars 57so that the coating is distributed within the interior of the cam 34 fora period of time equal to three incremental movements of the chain 11,in the form of the invention illustrated in FIGURE 1. Then, the feelerarms 56 contact a second bus bar 66 which supplies a lower voltage tothe motor 12, driving it at a lower rotational speed. This lower speedis sufficient to prevent sagging of the coating 67 along the walls ofthe can, but is not sufiicient to cause excessive turbulence during theheat treating cycle. The hardening is accomplished by playing openflames from a series of gas burners 68, 69 and 70 at the exterior of thecoated cans while the same are being rotated at the lower rotationalspeed. For a can which is /2 inch square in cross-section, suitablerotational speeds in this stage range from about 1000 to 3000 r.-p.m.

The temperature achieved in the coating through this exposure to theopen flame is sufiicient to set the plastisol into a self-sustainingcoating. As illustrated in FIGURE 4, this coating 67, due to thecentrifugal effects of the spinning operation, consists of a zone 71having a relatively high concentration of the iron particles, and a zone72 having a substantially lesser concentration of iron, and consistingprimarily of the resinous plastisol.

The apparatus of the present invention can be used to apply coatings ofvarying thickness in the container, as required. All that is necessaryis an adjustment of the amount of coating composition fed to the nozzle46 by the metering ejector 27.

While the apparatus of the present invention finds particular use forproviding a magnetic shield within a metallic container, it should beevident that the apparatus can also be used for insulating cans with adielectric material containing no ferromagnetic particles.

It should also be evident that various modifications can be made to thedescribed embodiments without departing from the scope of the presentinvention.

I claim as my invention:

1. An apparatus for coating the interior of a container with a heatsettable resinous composition which comprises conveyor means, rotatablework holder means on said conveyor for supporting a container thereon,electrical drive means for rotating each of said work holder means, saidconveyor means being arranged to deliver each work holder and thecontainer carried thereby successively through aninjecting station, ahigh speed rotation station, and a heating station, injecting means atsaid injecting station arranged to inject a predetermined amount of saidresinous composition into each container, a first electrical contactmeans positioned beyond said injecting station and engageable. by saidelectrical drive means to rotate said container at a high speed andthereby distribute said resinous composition as a film along theinterior'of said container, heating means at said heating station forsolidifying the film in said container, second electrical contact meansat said heating station engageable by said electrical drive means torotate said container at a lower speed during the heating thereof bysaid heating means, each of said electrical contact means consisting ofa pair of bus bars and each of said electrical drive means having feelerarms engageable with said bus bars.

2. The apparatus of claim 1 which said conveyor means is driven bylanintermittent drive means so that the container is stopped at saidinjecting station, said high speed rotation station, and said heatingstation.

3. The apparatus of claim 1 in which each of said work holders includescentrifugally operable clamping means which serve to clamp onto saidcontainer during high speed rotation thereof.

References Cited WALTER A. SCHEEL, Primary Examiner.

